The optimal number of cores depends on the "width of the road". When it is wide, the maximum available number is the best.
When it is not so wide, the optimal number may be lower. The Optimize test helps to directly find the optimal number.

Regarding the blog post, it discusses CPUs from the point of view of choosing a new CPU for the job. Usually, a CPU with more cores performs faster.
That is usually true even if the optimal number of cores (for Neat Video processing) is lower than the total number of cores.